Active organic electroluminescence panel display with blank layer covering contact opening

ABSTRACT

An active organic electroluminescence panel display and a fabricating method thereof are disclosed. A thin film transistor array comprising a plurality of thin film transistors, a plurality of datalines and a plurality of scanlines are formed on a substrate. A passivation layer is formed on the substrate, covering the thin film transistor array. A contact opening is formed in the passivation layer for exposing a prescribed area of the array. An anode layer is formed on the passivation layer and fills into the contact opening. A blank layer is formed on the anode, covering the contact opening. A shadow mask is disposed on the blank layer. Then, a sputtering process is performed to form an organic luminescent layer. The shadow mask is then removed, and a cathode layer is formed on the organic luminescent layer for forming an active organic electroluminescence panel display.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Taiwan applicationserial no. 92130175, filed on Oct. 30, 2003.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a display and a fabricating methodthereof, and more particularly to an active organic electroluminescencepanel display and a fabricating method thereof.

2. Description of the Related Art

Because of the shrinkage of semiconductor device and displays, portabledevices are now available to consumers. As to displays, cathode raytubes (CRT) dominate the market because of its high image quality andlow cost. However, because of space restriction, power consumption andenvironmental concern, CRT still has some issues that need to beresolved. Therefore, thin film transistor liquid crystal display, whichoffers high image quality, small space occupation, low power consumptionand radiation free, has gradually replaced CRT.

Flat panel displays include liquid crystal display (LCD), organicelectroluminescence display (OELD) and plasma display panel (PDP), etc.OELD, a dots matrix type display having emissive devices, has highbrightness, high efficiency, low weight, high effective contrast ratioand low power driving. The power consumption of OELD is less than thoseof CRT, PDP and LCD. Moreover, because its performance is independent ofred, green and blue lights, OELD is now deemed as the main trend for thenext generation of flat panel displays.

OELD includes active and passive drive displays depending on the drivingmodes. The service life and efficiency of the passive drive display willdecay depending on the size and resolution thereof. The active driveOELD has gradually replaced the passive type to date.

The active drive OELD includes thin film transistors (TFT) for drivingthe voltage required thereby. Generally, the process of fabricating theTFT can be varied depending on a position of an indium tin oxide (ITO)anode layer, e.g. on the top or the bottom of the source/drain terminals(ITO on Top and ITO on Bottom, respectively). The process also dependson the material used, such as polysilicon or amorphous silicon, which isapplied in the silicon layer. Referring to FIG. 1, during the process offabricating the polysilicon TFT substrate, the ITO is positioned on Topof the source/drain terminals, a contact opening 114 is formed withinthe passivation layer 106 on the dielectric layer 102 and thesource/drain 104. The ITO anode layer 108 is filled into the contactopening 114 for electrically connecting to the source/drain 104. A red,green and blue light organic luminescent layer 110 is configured on theITO anode layer 108 and the passivation layer 106. The cathode layer 112is configured on the organic luminescent layer 110. Because of the largestep height of the surface of the ITO anode layer 108 and thepassivation layer 106, particularly at the place marked A correspondingto the contact opening 114, and at the place marked B corresponding tothe edge of the source/drain 104, the thickness of the organicluminescent layer 110 thereof will be reduced and the cathode layer 112easily contacts with the anode layer 108 resulting in shorting.

Additionally, in the conventional method of forming the organicluminescent layer 110, the shadow mask directly contacts the anode layerand the passivation layer and the organic luminescent layer are formedthereon by sputtering. The shadow mask is then removed to repeat thesputtering process for several times to form the red, green and blueorganic luminescent layers on the anode layer and the passivation layer,respectively. During the sputtering processes, because the shadow maskis repeatedly made to come in contact to and then separated from the TFTsubstrate, damage will result therefrom adversely affecting theperformance of the device.

SUMMARY OF INVENTION

Therefore, an object of the present invention is to provide an activeorganic electroluminescence panel display and a fabricating methodthereof for avoiding the shorting of the anode and cathode layers at theplace corresponding to the contact opening and the edge of thesource/drain terminals.

The other object of the present invention is to provide an activeorganic electroluminescence panel display and a fabricating methodthereof for avoiding the damage resulting from the use of a shadow maskdirectly contacting the substrate for forming the organic luminescentlayer.

The present invention discloses an active organic electroluminescencepanel display, which comprises a thin film transistor array, apassivation layer, an anode layer, a blank layer, an organic luminescentlayer and a cathode layer. The thin film transistor array is configuredon a substrate, wherein the thin film transistor array comprises aplurality of thin film transistors, a plurality of scan lines and aplurality of data lines. The passivation layer is configured on the thinfilm transistor array, wherein the passivation layer comprises aplurality of contact openings exposing a prescribed area thereof. Theanode layer is configured on the passivation layer and fills into thecontact openings. The blank layer is configured on the anode layer andthe contact openings are covered thereby. The organic luminescent layeris configured on the anode layer. The cathode layer is configured on theorganic luminescent layer.

In a preferred embodiment of the present invention, the display furthercomprises a planarization layer on the blank layer. The planarizationlayer has a contact opening therein exposing a prescribed area of thethin film transistor. The anode is configured on the planarization layerand fills into the contact openings. The blank layer is configured onthe anode layer and the contact openings are covered thereby. The anodelayer is covered with the organic luminescent layer. The cathode layeris configured on the organic luminescent layer.

The present invention also discloses a method of fabricating an activeorganic electroluminescence panel display, which comprises: forming athin film transistor array on a substrate, wherein the thin filmtransistor array comprises a plurality of thin film transistors, aplurality scan lines and a plurality of data lines; forming apassivation layer over the substrate and covering the thin filmtransistor array; forming contact openings within the passivation layerfor exposing a prescribed area of the thin film transistor array;forming an anode layer on the passivation layer, filling within thecontact openings; forming a blank layer on the anode layer, covering thecontact openings; forming an organic luminescent layer over the contactopenings by disposing a shadow mask over the blank layer; removing theshadow mask; and forming a cathode layer on the organic luminescentlayer.

In a preferred embodiment of the present invention, the method furthercomprises forming a planarization layer on the blank layer and formingcontact openings therein for exposing a prescribed area of the thin filmtransistor. The anode is formed on the planarization layer and fills thecontact openings. The blank layer is on the anode layer and covers thecontact openings. The organic luminescent layer is formed over the anodelayer by disposing a shadow mask over the blank layer and by asputtering process. The shadow mask is then removed. The cathode layeris formed on the organic luminescent layer. Thus, the fabrication of theactive organic electroluminescence panel display is completed.

Accordingly, the present invention forms the blank layer at the placecorresponding to the contact openings and the edge of the source/drainterminals for planarizing the structure of the panel. The step height ofthe structure can be reduced and the shorting of the anode and cathodelayers resulting from the over-thick organic luminescent layer thereatcan be avoided. Additionally, the present invention uses the blank layerfor supporting the shadow mask during the deposition the organicluminescent layer. Therefore, the damage resulting from the contactbetween the shadow mask and the organic luminescent layer during thedeposition process thereof can be evaded.

In order to make the aforementioned and other objects, features andadvantages of the present invention understandable, a preferredembodiment accompanied with figures is described in detail below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a conventional activeorganic electroluminescence panel display.

FIGS. 2A-2F are a schematic manufacturing process flow of an activeorganic electroluminescence panel display of the present invention.

FIG. 3 is a schematic cross-sectional view showing an active organicelectroluminescence panel display according to another preferredembodiment of the present invention.

FIG. 4A is a top view of FIG. 2A and FIG. 2B.

FIG. 4B is a schematic top view showing an active organicelectroluminescence panel display according to a preferred embodiment ofthe present invention.

FIG. 4C is a schematic top view showing an active organicelectroluminescence panel display according to another preferredembodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing an active organicelectroluminescence panel display according to another preferredembodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing an active organicelectroluminescence panel display composed of amorphous silicon thinfilm transistors according to a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION

FIGS. 2A-2F is a schematic process flowchart illustrating a process offabricating an active organic electroluminescence panel displayaccording to a preferred embodiment of the present invention. FIG. 4A isa top view of FIG. 2A. FIGS. 2A and 2B are the cross-sectional viewstaken along I-I″ in FIG. 4A.

Referring to FIGS. 2A and 4A, a thin film transistor array 202 is formedon a substrate 200, wherein the thin film transistor array 202 comprisesa plurality of thin film transistors 204, a plurality of scan lines 206and a plurality of data lines 208. The thin film transistor 204 can be,for example, a polysilicon thin film transistor, which comprises asource terminal 210, a drain terminal 212, a channel 214, a gatedielectric layer 216 and a gate terminal 218. The scan lines 206 of thethin film transistor array 202 electrically connect with the gateterminal 218 and the data lines 208 electrically connect with the source210.

Moreover, in addition to being formed by one type of transistors, suchas the polysilicon thin film transistor, the array can be composed oftwo types of transistors, such as a CMOS transistor composed of a N-typeand a P-type transistor. Additionally, lightly doped drains (LDD) (notshown) can be formed within the polysilicon thin film transistor 204.

Referring to FIGS. 2B and 4A, a passivation layer 220 is formed over thesubstrate 200 and covers the thin film transistor array. The passivationlayer 220 can be, for example, silicon nitride and formed by a chemicalvapor deposition (CVD) process formed thereon. Then, a contact opening222 is formed within the passivation layer 220 for exposing a prescribedarea of the array, such as the source terminal 210 or the drain terminal212. The contact opening can be formed, for example, by performing aphotolithographic process and an etching process. An anode layer 224 isformed on the passivation layer 220 and fills within the contactopenings 222. The anode layer 224 can be formed, for example, bysputtering indium tin oxide (ITO) (not shown) on the passivation layer220, and patterning the ITO layer by performing a photolithographicprocess and an etching process. The slope sidewall of the anode layer224 is formed by controlling the etching parameters.

Referring to FIG. 2C, a photo-sensitive layer 226 is spin-coated on theanode layer 224 for planarizing the structure. The photo-sensitive layer226 has a thickness from about 0.5 μm to about 3 μm.

Referring to FIGS. 2D and 4B, the photo-sensitive layer 226 is patternedby a photolithographic process and an etching process for forming theblank layer 226 a covering the contact opening 222 and the edge of thesource terminal 210 or the drain terminal 212. The blank layer 226 a is,for example, a continuous pattern along direction of the scan lines 206.

Additionally, the blank layer 226 a can also be, for example, acontinuous pattern along direction of the data lines 208. Of course, theblank layer 226 a can be a non-continuous pattern, such as a blockpattern (not shown), on the anode layer 224 at the place correspondingto the contact opening 222 and the edge of the source terminal 210 orthe drain terminal 212.

Referring to FIG. 2E, a shadow mask 700 is disposed on the blank layer226 a for performing a deposition process, such as sputtering, forforming an organic luminescent layer 228 on the anode layer 224,covering the passivation layer 220 and the blank layer 226 a.

Referring to FIG. 2F, the shadow mask is then removed. A cathode layer230 is formed on the organic luminescent layer 228 and therebycompleting the fabrication of the active organic electroluminescencepanel display. The method of forming the cathode layer 230 can be, forexample, sputtering.

FIG. 2F is a schematic cross-sectional view of a single pixel of theactive organic electroluminescence panel display of the presentinvention. However, the pixel structure can use different organicluminescent layers 228 depending on the light emitted therefrom. Forforming R, G and B organic luminescent layers 228 on the anode layer224, the shadow mask should be used three times for performingdeposition processes thereof.

Referring FIGS. 2F and 4B, the active organic electroluminescence paneldisplay formed by the method described above comprises the thin filmtransistor array 202, the passivation layer 220, the anode layer 224,the blank layer 226 a, the organic luminescent layer 228 and the cathodelayer 230. The thin film transistor array 202 is formed on the substrate200 and comprises plurality of thin film transistors 204, a plurality ofscan lines 206 and a plurality of data lines 208. The thin filmtransistor 204 can be, for example, a polysilicon thin film transistor,which comprises the source terminal 210, the drain terminal 212, thechannel 214, the gate dielectric layer 216 and the gate terminal 218.The passivation layer 220 is over and covers the thin film transistorarray 202. The contact opening 222 is formed within the passivationlayer 220 for exposing a prescribed area of the array, such as thesource terminal 210 or the drain terminal 212. The anode layer 224 isformed on the passivation layer 220 and fills within the contact opening222. The blank layer 226 a is on the anode layer 224 and covers thecontact opening 222 and the edge of the source terminal 210 or the drainterminal 212. The organic luminescent layer 228 is on the anode layer224. The cathode layer 230 is formed on the organic luminescent layer228.

In another preferred embodiment, a planarization layer is formed forincreasing the opening ratio of the display before forming the anodelayer. Referring to 3, a planarization layer 232 is formed on thepassivation layer 220 after the passivation layer 220 is formed on thethin film transistors array. The planarization layer 232 can be, forexample, an organic material. A contact opening 220 a is then formedtherein for exposing the source terminal 210 or drain terminal 212. Theanode layer 224 is formed on the planarization layer 232 and fillswithin the contact opening 222 a for electrically connecting the anodelayer 224 and the source terminal 210 or drain terminal 212. The blanklayer 226 a is formed on the anode layer 224 at the place correspondingto the contact opening 222 a and the edge of the source terminal 210 ordrain terminal 212 which are along the data line or scan line. Theorganic luminescent layer 228 is on the anode layer 224 and covers theplanarization layer 232 and the blank layer 226 a. The cathode layer 230is formed on the organic luminescent layer 228. Thus, the active organicelectroluminescence panel display is formed.

In addition to being applied to the active organic electroluminescencepanel display formed by polysilicon thin film transistors, the presentinvention can be also applied to the active organic electroluminescencepanel display composed of amorphous silicon thin film transistors.

Referring to FIGS. 5 and 4A, the thin film transistor array 202 isformed on the substrate 900 and comprises a plurality of thin filmtransistors 204, a plurality of scan lines 206 and a plurality of datalines 208. The thin film transistor 204 can be, for example, anamorphous silicon thin film transistor, which comprises the sourceterminal 910, the drain terminal 912 and the channel 914. The scan line206 of the thin film transistor array 202 electrically connects with thegate terminal 914 and the data line 208 electrically connects with thesource terminal 910. The passivation layer 220 is formed and covers thethin film transistor array 202. The contact opening 222 is formed withinthe passivation layer 220 for exposing the source terminal 910 or thedrain terminal 912. The anode layer 224 is formed on the passivationlayer 220 and fills within the contact opening 222 for electricallyconnecting the anode layer 224 and the source terminal 910 or the drainterminal 912.

Referring to FIGS. 4B, 4C and 5, the blank layer 226 a is formed on theanode layer 224 and covers the contact opening 222 and the edge of thesource terminal 910 or the drain terminal 912. The organic luminescentlayer 228 is formed on the blank layer 226 a for covering thepassivation layer 220 and the anode layer 224. The cathode layer 230 isformed on the organic luminescent layer 228. Finally, the active organicelectroluminescence panel display is formed.

Similarly, a planarization layer 232 can also be formed on thepassivation layer 220 for increasing the opening ratio of the displaycomposed of amorphous thin film transistors as shown in FIG. 6.Referring to 4B, 4C and 6, the planarization layer 232 is formed on thepassivation layer 220 after the passivation layer 220 is formed on thethin film transistors array 902. The planarization layer 232 can be, forexample, an organic material. A contact opening 220 a is then formedtherein for exposing the source terminal 910 or drain terminal 912. Theanode layer 224 is formed on the planarization layer 232 and fillswithin the contact opening 222 a for electrically connecting the anodelayer 224 and the source terminal 910 or drain terminal 912. The blanklayer 226 a is formed on the anode layer 224 at the place correspondingto the contact opening 222 a and the edge of the source terminal 910 ordrain terminal 912 which are along the data line or scan line. Theorganic luminescent layer 228 is on the anode layer 224 and covers theplanarization layer 232 and the blank layer 226 a. The cathode layer 230is formed on the organic luminescent layer 228. Finally, the activeorganic electroluminescence panel display is formed.

The present invention forms a blank layer on the passivation layer atthe place corresponding to the contact openings or having an obviousstep height for avoiding the shorting of the anode and cathode layersresulting from the over-thick organic luminescent layer thereat.

Additionally, the present invention uses the blank layer for supportingthe shadow mask during depositing the organic luminescent layer.Therefore, the shadow mask does not directly contact with the organicluminescent layer or the anode layer. The damage resulting from thecontact between the shadow mask and the organic luminescent layer duringthe deposition process thereof can be evaded.

Although the present invention has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be constructed broadly to include other variants and embodimentsof the invention which may be made by those skilled in the field of thisart without departing from the scope and range of equivalents of theinvention.

1. An active organic electroluminescence panel display, comprising: athin film transistor array on a substrate, wherein the thin filmtransistor array comprises a plurality of thin film transistors, aplurality of scan lines and a plurality of data lines; a passivationlayer on the thin film transistor array, wherein the passivation layercomprises a contact opening exposing a prescribed area thereof; an anodelayer on the passivation layer, filling within the contact opening; ablank layer on the anode layer, covering the contact opening; an organicluminescent layer on the anode layer and an area of the passivationlayer which are uncovered by the anode layer and the blank layer; and acathode layer on the organic luminescent layer.
 2. The active organicelectroluminescence panel display of claim 1, wherein the blank layerincludes a photo-sensitive material.
 3. The active organicelectroluminescence panel display of claim 1, wherein the blank layerhas a thickness from about 0.5 μm to about 3 μm.
 4. The active organicelectroluminescence panel display of claim 1, further comprising aplanarization layer on the passivation layer, the contact opening formedwithin the passivation layer and the planarization layer.
 5. The activeorganic electroluminescence panel display of claim 4, wherein theplanarization layer is an organic material.
 6. The active organicelectroluminescence panel display of claim 1, wherein a sidewall of theanode layer is a slope.